1. Field of the Invention
The present invention relates to a circuit arrangement for telecommunications systems, particularly telephone exchange systems, comprising a centralized and/or partially-centralized information-processing sequential logic systems having a limited call-in capability with respect to the information processing capacity, and comprising measuring circuits for identifying the loadability of such sequential logic systems, these integrating the constantly-fluctuating load over time intervals that are sufficiently long in order to assure an identification result having sufficient accuracy. Further, counters are provided for the identification of the information processing traffic load of a respective sequential logic system, for the recognition of information-processing traffic overloads and for averting such overloads, whereby the counter supply respectively current momentary value of the information-processing traffic load with the shortest possible time delay in order to realize a defense against overloads with a short time delay.
2. Description of the Prior Art
A circuit arrangement of this general type is already known from a lecture that was held at the "9.sup.th INTERNATIONAL TELETRAFFIC CONGRESS (ITC)" in October 1979 at Torremolinos, Spain (Conference paper ITC-9 by SOMOZA et al, pp. 1-7). In arrangements known from this lecture, therefore, a differentiation is undertaken between a loadability measurement, on the one hand, supplying an identification result pertaining to the loadability of a central sequential logic system, and an information-processing traffic load identification, on the other hand, indicating the respective current state of the traffic load. Whereas the identification result levels short-duration fluctuations in the traffic load, the result of the continuing information-processing traffic load identification should be as current as possible, i.e. supply a respective result in which the on-going load fluctuations are expressed. The identification result of the loadability measurement specifies a measurable variable to which the continuously-identified, current result of the information-processing traffic load is compared. The result of the loadability measurement is a guide line, i.e. a reference value, for that traffic load to be supplied to a central control unit. The result of the information-processing traffic load identification is the respective current actual value of the traffic load existing at every moment. Comparison of this actual value to the reference value provides a respective indicator as to whether the traffic load to be routed to the central control unit can be increased with respect to the momentary value or must be reduced.
In the above known instance, the loadability measurement for the acquisition of the reference value occurs by tallying service requests forwarded to a sequential logic system over relatively long time intervals of a number of seconds each, whereas the load measurement for identifying the on-going actual values likewise occurs by tallying, but in far shorter time intervals, whereby each of these time intervals is only a small fraction of each of the aforementioned time intervals. When this tally within a time interval exceeds a limiting value corresponding to and defined by the reference value, then all further requests up to the end of the time interval are not accepted. The load of a sequential logic system is therefore controlled with individual requests to be executed (arithmetic operations, control events and the like). It is thereby necessary to make each of the time intervals sufficiently long so that a load regulation does not occur in coarse skips, occuring, rather, sufficiently fine. The number of requests and, therefore, the in-flow of information to be processed in the computer can be restricted, or even temporarily stopped, entirely on the basis of the load results acquired by the tallying operation. The traffic load is thereby to be optimally matched to a call-handling capability and overload limits of the computer in order to therefore achieve as high as possible the utilization of the computer capacity, as well as avoiding overloads insofar as possible, such overloads, as known, resulting in considerable temporary operations restrictions or operations malfunctions for the devices making use of the computer. This is therefore alleviated in the cases of use addressed in the conference paper by way of a dynamic matching of the traffic load of computer requests to the computer based on changing type and, therein, on frequency.
The known methods for recognizing and regulating the computer traffic load, however, supply an adequately accurate result only when the individual time interval employed for counting the events, for example computer requests, is sufficiently large with respect to the mean chronological spacing between these events so that fluctuations in the computer traffic load, the load rising and falling continuously, do not cause the computer traffic load to be represented in course skips so that the corresponding control is capable of optimally matching the computer traffic load to the loadability. The requirement inherent therein, namely that the time interval for the individual tally of the events must be sufficiently long, has a negative effect on the respective point in time at which the results of each of the tally operations are available. The result of identifying the computer traffic load, therefore, still always exhibits a time lag that is necessarily conditioned by the fact that the corresponding result for each acquisition time interval is identified only after the time interval has elapsed, being identified, in particular, by way of a comparison operation. This time lag is, in turn, disadvantageous to influencing the computer traffic load for the purpose of regulating the same. For, in particular, either averting an overload can only take effect when the overload situation has already occurred, i.e. to late in view of actually-arising overloads, or the aversion of an overload must already begin before the overload limit of the computer has been reached at all, i.e. "under suspension", therefore not only in those operating instances in which the computer traffic load in fact rises above the loadability limit, but in addition, in all of those operating instances as well in which the rise of the computer traffic load in the direction toward the loadability limit only produces the assumption that the loadability limit will be transgressed, but in which the computer traffic load does not, in fact, reach or exceed the loadability limit. The problem therefore lies in the extrapolation of the load behavior over the time. A regulation, however, is less and less effective the later it begins; its relatively late beginning, in addition, can result in the fact that periods of more pronounced under utilization continuously alternate with periods of overloads without this actually being caused by the traffic load that in fact occurs. The requirement is further amplified by the condition that the chronological distribution of the events to be acquired scatters noticeably, that, therefore, the chronological spacings between the respectively-successive events are relatively unequal in comparison to one another. The effect is all the more aggravated the smaller the respective acquisition range; the greater this range, the greater the influence of the compensating effect of the statistical distribution. The size of the aforementioned time intervals, therefore, also has a delaying influence on the respective beginning of the regulation effect and, therefore, on the effectiveness of the regulation. The duration of each of the time intervals must be selected all the greater, the smaller the number of requests occurring per time unit. This duration, therefore, is longer given, for example, partially-centralized control units that are assigned to a central control unit than at the central control unit itself when one proceeds on the basis that the number of requests per time unit is higher at the central control unit than at the partially-centralized control units.